Dragon feed and potions fall into this category.
Equipment could be equipped by dragons. When equipped they raise dragon's status. Claws, feathers, charms, etc. could be found in this category.
Gems could be equipped by dragons. The maximum is 3 gems for each dragon. Equip-able gem types depends on the dragon's gem slot color.
All dragon eggs obtained are found in this category.
Skill scrolls are used to teach dragons skill.
Unused maps all belong in this category.
Used in the lavatory for making dragon eggs.
All other items, which doesn't belong to any other categories, falls into this category.